Gd-modified Mn-Co oxides derived from layered double hydroxides for improved catalytic activity and H2O/SO2 tolerance in NH3-SCR of NOx reaction.

Metal oxides derived from layered double hydroxides (LDHs) are expected to obtain low-temperature denitrification (de-NOx) catalysts with high catalytic activity and H2O/SO2 tolerance in the selective catalytic reduction (SCR) of NOx with NH3. In current work, we successfully prepared Gd-modified Mn-Co metal oxides derived from Gd-modified Mn-Co LDHs. The resultant Gd-modified Mn-Co metal oxides exhibit excellent catalytic activity and high H2O/SO2 tolerance in the NH3-SCR de-NOx reaction. The reasons for the enhancement can be ascribed to the unique surface physicochemical properties inherited from LDHs and the modification of Gd, which increase the specific surface area, improve the relative content of Mn4+ and Co3+ on the surface, enhance the number of acidic sites, strengthen the reducibility of catalyst, resulting in the enhanced catalytic activity and H2O/SO2 tolerance. Additionally, it is demonstrated that the NH3-SCR de-NOx reaction occurred on the surface of Gd-modified Mn-Co oxides followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. This study provides us with a design approach to promote catalytic activity and H2O/SO2 tolerance through morphology control and rare earth modification.

Efficient degradation of Congo red and phenol by a new photocatalyst Ag/AgBr-Al-attapulgite composite under visible light irradiation.

Nowadays the concern on the treatment of refractory organic pollutants (e.g., Congo red and phenolic compounds) in industrial wastewaters and their treated effluents with conventional technologies has been still continuously increasing. In this study, a novel visible light photocatalyst material, Ag/AgBr and Al loading on the attapulgite (ATP), was prepared for efficiently catalyzing the photodegradation of the two refractory substances, and its photocatalytic performance and recyclability were assessed. Results from transmission electron microscopy and X-ray diffraction confirmed the successful loading of Ag/AgBr and Al on the ATP. The prepared Ag/AgBr-Al-ATP composite presented substantially better catalytic performance than Ag/AgBr alone probably because the ATP as a carrier of catalyst provided more contact surface for catalyst Ag/AgBr and Congo red/phenol. In the Ag/AgBr-Al-ATP composite, the photocatalyst AgBr content increased from 20.4 to 34.9% due to the modification of ATP by Al. Correspondingly, the Ag/AgBr-Al-ATP composite presented its excellent photocatalytic performance under visible light irradiation: photodegradation efficiencies of Congo red and phenol of 1.73 mg/100 mg and 0.86 mg/100 mg were achieved. With the increase of pH, the photolysis efficiencies of Congo red and phenol both first increased and then decreased, whereas the optimal photocatalytic performance occurred at pH 7 for Congo red and pH 10 for phenol. The Ag/AgBr-Al composite presented a high catalytic activity for photolysis of Congo red and phenol in all the four consecutive reused cycles. The results in this study comprehensively demonstrated a promising photocatalyst for efficient removal of the similar refractory organics presented in industrial wastewaters, which deserves further investigation and development.